The invention relates to a method and apparatus for testing physical integrity of production tubing and production casing in gas-lift well systems.
The production of hydrocarbons from subterranean formations results in a reduction of pressure in the formation. This formation pressure drives the production of the hydrocarbons during the primary production period of the well, by providing a pressure differential which forces fluids to be produced up out of the well and into the various flow lines located at the surface of the well. When the pressure at the formation drops to the point where it can no longer drive the production of hydrocarbons to the surface, secondary techniques are frequently used to provide the necessary energy to the hydrocarbons to bring them to the surface. One method of secondary recovery, called gas-lift, is carried out by injecting gas into the production tubing at various points to increase the subsurface pressure and drive the production of fluids to the surface.
In situations where gas-lift is to be used, regulations frequently require that the system be tested to ensure an absence of leaks from the well into surrounding formations such as aquifers. Further, because the gas used to drive the production has a value, and because the gas may contain components which are harmful to the crew working the well, additional incentive exists for ensuring the integrity of both production tubing and production casing of the well to which gas-lift is to be applied.
Various technologies are known in the art which provide methods for testing integrity of the production tubing. These procedures, however, cannot be used to test the integrity of the casing of the well without removal of either the production tubing or various gas-lift equipment which may be affixed to the production tubing. Removal of this equipment, (mandrels, for example, through which gas passes into the production tubing), requires increased down time of the producing well, as well as the use of technologically trained personnel, resulting in prohibitive costs.
U.S. Pat. No. 4,182,159 discloses a pressure testing tool which can be activated at a desired location in tubing in order to allow pressure testing of a particular section of the tubing. No disclosure is made, however, of any method to be used for such pressure testing.
It is, accordingly, a principal object of the present invention to provide a method and apparatus for testing the physical integrity of production tubing and production casing wherein integrity of the production casing can be tested and removal of gas-lift hardware such as mandrels and other completion equipment is minimized.